1. Field of the Invention
The present invention relates to a vibration correction apparatus or image pickup apparatus having a vibration correction function of correcting camera shake, vibrations, and the like.
2. Related Background Art
In a compact video camera or the like, an object image is blurred due to camera shake, vibrations, and the like and is often not easy to see. In particular, since a recent video camera adopts a large-magnification lens, the image is considerably blurred at the telephoto side.
To solve this problem, many vibration correction apparatuses for correcting vibrations such as camera shake and the like have been proposed and are commercially available. As a vibration correction method using an optical system, a prior art that uses an angular velocity sensor as a vibration detection means, and a variable angle prism (VAP) as an image correction means is known. This prior art will be explained below.
The VAP will first be explained. As shown in FIG. 2, the VAP is made up of two opposing glass plates 21 and 22, bellows 23 and 24 that connect the two glass plates, and a high-refraction liquid 25 that fills a space closed by the bellows. Rotation shafts 26 and 27 are respectively provided to the glass plates 21 and 22.
In FIG. 2, when one glass plate 21 rotates by a about the rotation shaft 26, an incoming light beam 28 is deflected by xcfx86 owing to the same principle as a wedge prism. Likewise, the other glass plate 22 can rotate about the rotation shaft 27 and can deflect an incoming light beam 28.
The VAP with the above arrangement removes blurring of or stabilizes the object image by simultaneously controlling the two glass plates 21 and 22. In this example, upon filtering a signal output from the angular velocity sensor, the DC component is cut from that signal by a DC cut filter, and the signal is amplified by a predetermined amount for the purpose of camera shake correction. Thereafter, the signal is subjected to predetermined filtering to obtain a target value of the apex angle of the VAP. In accordance with this target value, the apex angle of the above-mentioned VAP is varied to attain camera shake correction.
However, the signal output from the angular velocity sensor has lower sensitivity as the frequency becomes lower, and its phase in the low-frequency band is not ideal as a result of signal processing. Hence, the user may feel poor effects in the low-frequency range especially at a large magnification.
Motion of images between fields is detected from the sensed image, and low-frequency range performance is improved by using the image motion information in addition to the above-mentioned VAP mechanism. However, since the sampling period of image motion detection is long, if the target value is updated at such long periods, the sensed image appears to have lower resolution.
The present invention has been made to solve the above-mentioned problems, and has as its first object to provide a vibration correction apparatus which is free from any resolution drop over the entire frequency range.
It is the second object of the present invention to optimize the characteristics of a vibration correction apparatus, which performs vibration detection and correction using both a physical sensor such as an angular velocity sensor and image motion information.
It is the third object of the present invention to provide a vibration detection and correction apparatus which has high correction effects for every vibration components ranging from lower to higher frequencies, and is free from any resolution drop.
In order to achieve the first to third objects, according to a preferred embodiment of the present invention, there is disclosed a camera comprising:
optical motion correction means for optically correcting motion of an image;
electronic motion correction means for electronically correcting the motion of the image;
electronic zoom means for electronically enlarging the image; and
control means for, when the electronic zoom means is inactive, controlling to selectively operate the optical motion correction means and the electronic motion correction means, and for, when the electronic zoom means is active, controlling to operate both the optical motion correction means and the electronic motion correction means.
According to a preferred embodiment of the present invention, there is also disclosed an image pickup apparatus comprising:
vibration detection means for detecting vibration of a device;
motion detection means for detecting image motion from an image signal;
vibration correction means for correcting vibration of an image in accordance with one or both of output signals from the vibration detection means and the motion detection means;
signal processing means for calculating a correction target value to be supplied to the vibration correction means on the basis of a motion vector signal detected by the motion detection means; and
sampling period varying means for setting a sampling period of the correction target value calculated by the signal processing means to be shorter than a sampling period of the motion vector signal.
It is the fourth object of the present invention to optimize the processing speed of the system.
In order to achieve the fourth object, according to a preferred embodiment of the present invention, there is disclosed an image pickup apparatus comprising:
an image pickup element;
rewritable storage means;
first signal processing means for processing a video signal from the image pickup element, and writing the processed video signal in the storage means at a first rate;
second signal processing means for reading out the video signal from the storage means at a second rate; and
function control means for controlling a function associated with imaging on the basis of a signal from the first signal processing means,
wherein the first rate is set to be higher than the second rate.
Other objects and features of the present invention will become apparent from the following description of the specification and the accompanying drawings.